Problem: $ { \left[\begin{array}{rr}{3} & {-1} \\ {0} & {3}\end{array}\right]+\left[\begin{array}{rr}{4} & {2} \\ {-2} & {-1}\end{array}\right] = {?} } $
Explanation: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{3}+{4} & {-1}+{2} \\ {0}+{-2} & {3}+{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{7} & {1} \\ {-2} & {2}\end{array}\right]}$